1. Field of the Invention
The present invention is directed to a cable for use in providing connections to sensors. More particularly, the invention provides an interface cable for connecting a sensor to a power source and for conveying an output from the sensor to a control device.
2. Description of Related Prior Art
Sensors are used for a variety of applications including sensing the presence or absence of articles and sensing a distance or proximity of an article to the sensor, such as may be required for a process control application. In particular, ultrasonic sensors are widely used for numerous sensing applications for process control of production and packaging operations. Such sensing applications include container presence/absence detection, container size detection, product level detection, container orientation detection, container counting operations, material web control, tamper/safety seal detection, surface coating detection, as well as many others. Typically, specification of sensors at particular locations on a production or process machine is an integral part of the control system design to enable the machine to operate as intended.
Ultrasonic sensors require a power source and include a pair of power input connections for powering the sensor, and additionally include a pair of sensor output connections for providing an output to a controller for detecting the signal from the sensor. Further, the sensors are either configured to operate with an AC power source or a DC power source with a corresponding sensor output connection, where the output connection for the AC sensor is a switching output which is either normally open or normally closed, and the output connection for the DC sensor is either a current sourcing output on one of the output lines or a current sinking output on the other of the output lines.
Production or process machines incorporating sensors are often designed with wiring for the sensors built into the structure of the machine to facilitate power connection to the sensor and to provide sensor output connections to a process controller. However, when an application requires the use of DC sensors on a machine wired for AC sensors, or the provision of DC power from an AC source, it is necessary to convert the power supply and the sensor output to be compatible with the existing wiring. In the past, this has typically required installation of equipment, such as separately mounted equipment boxes, for providing conversion from AC power to DC power and for providing a conversion of the DC sensor output to make the output compatible with the AC sensor leads to be operative with the process controller wired to the sensor leads.